1. Field of the Invention
The present invention relates to a detection protection technology for fluorescent electronic ballasts.
2. Description of the Related Art
Fluorescent lamps have excellent power saving features, and have gradually become the mainstream lamps, replacing the traditional incandescent lamp. There is a difference between the fluorescent lamp and the incandescent lamp, which is that the fluorescent lamp has to be used with electronic ballast for producing high voltage for ionizing gas in the lamp.
FIG. 1 is a schematic diagram of an electronic ballast 100 of the prior art. As shown in FIG. 1, the electronic ballast 100 is coupled to the fluorescent 110, and comprises: a filter circuit 102, a rectifier circuit 104, a power factor correction circuit 106 and an inverter circuit 108. The filter circuit 102 can filter out high frequency noise from an alternating current power supply. The rectifier circuit 104 can convert the alternating current power supply into a direct current power supply. The power factor correction circuit 106 can increase power factor and reduce harmonics. The inverter circuit 108 can produce the high-frequency alternative power supply for the fluorescent. Note that when the power supply is turned off and its voltage drops, the high voltage electrolytic capacitors in the power factor correction circuit 106 still keep providing power to the inverter circuit 108 and the fluorescent 110. As such, the inverter circuit 108 will become an inductive load rather a capacitive load (see the relationship between the voltage and the current of the inverter circuit 108 as shown in FIG. 2), thus increasing the possibility of breaking down the power semiconductor switching units and the control chip of the inverter circuit 108.
Therefore, the present invention provides a new fluorescent electronic ballast, which can prevent damaging power semiconductor switching units and control chip in an inverter circuit of the electronic ballast, thus prolonging the lifetime of the fluorescent lamp.